The present invention relates to devices and methods for treating patients suffering from renal diseases.
The leading causes of death in patients with End Stage Renal Disease (ESRD) are cardiac related. Cardiac related diseases include acute myocardial infarction, cardiac arrest, cardiac arrhythmia, cardiomyopathy, atherosclerotic heart disease, valvular, pericarditis, and pulmonary edema. These diseases account for 43% of all deaths in this population or roughly 17,000 deaths per year (United States Renal Data System, USRDS).
ESRD patients have a high prevalence of cardiac disease due to their inability to excrete fluids. In individuals with normal renal function, the blood is filtered and toxins and fluids are removed as necessary. Since ESRD patients are not capable of sufficiently excreting fluids, water and other fluids which are consumed remain in the body until they are removed by ultrafiltration (removal of excess fluid from the body) during dialysis.
The body's fluid retention mechanism tends to be consistent from patient to patient. The blood volume is usually first to expand. The blood volume is known to increase in size by as much as 20%. This places undue stress on the heart and the circulatory system as is evident by the rise in blood pressure and concurrent incidence of heart failure in ESRD patients. When the extracorporeal system is at its maximum fluid capacity (related to oncotic and osmotic forces), the fluid then distributes throughout the body, usually ending up in the extremities such as ankles, hands and other tissues as edema. The total quantity of fluid which the body can hold varies from patient to patient, however volumes as large as 7 liters, or 15 pounds, of fluid are common. The result of this fluid overload is reflected in increased hypertension and edema. If the body continues to take on more fluid, the fluid then enters the pleural cavities and the patient has shortness of breath. Oxygen uptake in the lungs is reduced as air in the alveoli becomes displaced by water. If this condition is not treated, death can result. The treatment currently employed is ultrafiltration.
Once the fluid is removed and the proper dry weight of the patient is reached, blood pressure will drop and breathing will return to normal. However, repeated increases and decreases in blood volume are believed to inflict damage to the heart and vascular system, thereby increasing the risk of cardiac disease.